1. Field of Invention
The present invention relates to a polysiliocn layer and a method of forming the same, and more generally to a polysiliocn layer with different grain sizes and a method of forming the same.
2. Description of Related Art
As the design rule of a semiconductor device is scaled down, the standard for the flatness of the gate is accordingly increased. The gate is usually formed from polysilicon by a chemical vapor deposition (CVD) process. It is found that when the surface of the polysilicon layer is not flat enough, the surface roughness (Rq and Ra) of the polysilicon layer and the sheet resistance (Rs) uniformity within a wafer are affected, and the performance of the device is degraded.
Therefore, how to form a uniform polysilicon layer to improve the device performance has been one of the main topics in the industry.